FIG. 5 is a block diagram showing a configuration of a conventional inverter apparatus. In the drawing, numeral 10 is an inverter main circuit, and numeral 11 is a converter part for converting an AC voltage into a DC voltage, and numeral 12 is a capacitor for smoothing a DC voltage, and numeral 13 is an inverter part, which comprises a transistor and a diode, for converting a DC voltage into an AC voltage, and the inverter main circuit 10 comprises the converter part 11, the capacitor 12 and the inverter part 13. Numeral 14 is a motor driven at a variable speed by an output from the inverter part 13. Also, numeral 20 is an inverter control circuit which has an interface to the outside and controls the inverter part 13, and numeral 21 is nonvolatile memory, and numeral 22 is an operating panel for performing setting and display of a frequency or a parameter etc., and numeral 30 is a microcomputer (hereinafter referred to as CPU) which is respectively connected to the nonvolatile memory 21 and the operating panel 22 and performs various calculations based on information inputted from the operating panel 22 and information stored in the nonvolatile memory 21.
Also, the operating panel 22 comprises a display part 23 for displaying data, a key group 24 for performing a selection, a modification, a determination of data, operations of a run and a stop of the inverter apparatus and so on, and a variable resistor 25 for changing and outputting a voltage from 0 V to 5 V according to a rotation angle.
Also, in the CPU 30, numeral 31 is key input means for reading an on-off signal given from the key group 24 on the operating panel 22, and numeral 32 is variable resistance value input means for detecting and digitizing an analog value inputted from the variable resistor 25 on the operating panel 22, and numeral 33 is control panel control means for analyzing an input signal obtained from the key input means 31 and the variable resistance value input means 32 and outputting data according to an input from the outside, and numeral 34 is display means for controlling the display part 23 on the operating panel 22.
Numeral 35 is inverter control means for performing controls of a start, a stop, a change in an output frequency, etc. of the inverter apparatus by performing on-off control of the transistor of the inverter part 13 based on information obtained from the control panel control means 33, and the inverter control means creates data outputted to the display part 23 of an output frequency, an output current, etc. and delivers the data to the control panel control means 33.
Also, numeral 36 is memory communication means for reading and writing data of the nonvolatile memory 21, and the control panel control means 33 requires reading and writing of data of the nonvolatile memory 21 to the memory communication means 36 as necessary.
The CPU 30 comprises the key input means 31, the variable resistance value input means 32, the control panel control means 33, the display means 34, the inverter control means 35 and the memory communication means 36 previously constructed in the inside by software.
Next, operations of the conventional apparatus will be described.
When a voltage is supplied from a power source to the inverter apparatus, the CPU 30 reads data of the nonvolatile memory 21 by the memory communication means 36 and outputs proper data to the display part 23 by the control panel control means 33 based on information on the corresponding parameter. It is constructed so that an inverter output frequency is normally displayed on the display part 23 and the present state (run state, stop state) of the inverter apparatus or for the run state, what frequency (Hz) the inverter apparatus runs with is recognized.
When the output frequency is modified, there are two patterns of the case of making a modification with an analog value by the variable resistor 25 and the case of making a modification with a digital value by key operations of a “Δ” key and a “V” key (not shown) in the key group 24. These two patterns of a run mode can be selected by a “run mode switching” key (not shown) in the key group 24.
When the output frequency is modified by the variable resistor 25, an analog run mode is first selected by the “run mode switching” key. The information is delivered from the key input means 31 to the operating panel 22 and a modification of the run mode is made according to an internal state of the inverter control means 35. When the variable resistor 25 is next operated (a frequency setting value increases in the case of rotating in a clockwise direction at the time of frequency setting), the variable resistance value input means 32 detects a voltage inputted from the variable resistor 25 and makes a conversion to a digital value in the inside. The digitized data is delivered to the control panel control means 33 and is converted into a setting frequency value according to calibration value data previously stored in the nonvolatile memory 21.
When the output frequency is modified by the setting in the variable resistor, the output frequency reaches a setting value at constant acceleration or deceleration time after the setting in the variable resistor, so that a phenomenon in which an overshoot occurs to a target value or an undershoot occurs in an attempt to set again further and thus it is quite difficult to set the value to the target value tended to occur. Also, when the output frequency is modified by the setting in the variable resistor, it was difficult to fix the value exactly to a round value such as 60.0 Hz.
Also, when a setting frequency is set with a digital value, in a manner similar to the above, the run mode is first switched to a digital run mode and next, a display/operation mode is modified from a monitor mode to a frequency setting mode by an operation of pressing a “MODE” key (not shown) for making a transition of a state of the operating panel and so on. Then, a value is modified by a “Δ” key and a “∇” key in the key group 24. Since the value during the modification is displayed on the display part 24 at any time, an operator modifies a setting value by pressing the “Δ” key and the “∇” key while watching the value on the display part 24 and sets the setting value to an arbitrary value and thereafter, the value is determined by an operation of pressing a “SET” key (not shown) for determining a numerical value after the modification and so on.
The control panel control means 33 reads the contents which the operator inputs by the operating panel 22 through the key input means 31 and the volume input means 32 at any time. For example, the control panel control means 33 delivers information to the inverter control means 35 when detecting that a start command of the inverter apparatus has been inputted by a signal from the key input means 31, and the inverter control means 35 starts calculations of an output frequency and an output voltage. Also, when a change in input of an analog voltage is detected by the volume input means 37, the control panel control means 33 changes a setting frequency according to an analog signal and delivers information to the inverter control means 35, and the inverter control means 35 changes an output frequency and an output voltage according to the setting frequency.
For setting of an output frequency by a key, first, the key group 24 has a “MODE” key for making a transition of mode states such as an output frequency monitor mode, a frequency setting mode or a parameter setting mode (not shown), and the key input means 31 sends the information to the control panel control means 43 whenever the “MODE” key is inputted. In the frequency setting mode, the present setting frequency is first displayed on the display part 23 and when a “Δ” key and a “∇” key are inputted, the key input means 31 measures time in which the key has been pressed or the number of times in which the key is pressed, and delivers the amount of change to the control panel control means 33. The control panel control means 33 calculates the rate of change Δf in the frequency corresponding to the amount of change, and adds the rate of change to the present setting frequency, and delivers data to the display means 34, and outputs character data converted there to the display part 23. Then, when a “SET” key having meaning of a determination in the key group 24 is inputted, the information is sent to the control panel control means 33 through the key input means 31 and the control panel control means 33 updates the setting frequency to the present data. The updated setting frequency data is delivered to the inverter control means 35, and an output frequency in response to acceleration or deceleration time is calculated every cycle time of software processing. Then, the output frequency is converted into a signal for turning on or off the transistor of the inverter part 13 inside the inverter control means 35 and is finally outputted to the inverter part 13.
In the conventional inverter apparatus as described above, there was a problem that it is difficult to fix a value exactly to a frequency setting value speedily in the case of setting of an output frequency by the variable resistor. Also, in the case of digital setting, there was a problem that it is necessary to modify a setting value by a “Δ” key and a “V” key after switching to a frequency setting mode once.
This invention is implemented to solve the problems as described above, and an object of the invention is to easily and speedily modify an output frequency of an inverter apparatus and eliminate a fluctuation in the output frequency due to an overshoot in the case of modifying the output frequency.
Also, when a setting value is modified by a variable resistor, an object is to easily and speedily perform the operations.